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rich PDF generation framework in java

I have hundreds of rich PDFs that need to be generated from my application, they have images and colorful content. I was looking to build a framework which support a template and data model and can take care of rest, so adding anew pdfs would be just adding a new template. In the past i have used free-marker to generate HTML and that print HTML to PDFs, are there any better recent solution to solve this problem?

There are various things you could do:
generate xml data, apply xslt transformation to style it, and convert
the html document to a pdf
code a small class that converts whatever data format you have to a pdf document (you would need to do all the layout through code)
create a template (using whatever design program you want) pdf document, insert form fields, and have iText fill the form (several of our customers go for this approach)
Keep in mind that JasperReports uses a proprietary format. Whereas the approaches I suggested use only open and well-established formats.

Take a look at JasperReports.

How to generate a xslt file from xml

I'm beginner with xml and xsl. I'm looking for the way to generate or understanding how is the using of xsl stylesheet. In my particular case, I'm using a html file which it converts to xhtml. The next step I want to convert is the file generated to xsl-fo but I've seen I have to use a xslt stylesheet to do that. My question is about this file. How is it generate this xsl file? Is generated from the xhtml file?
Thanks!

Antenna House provides a sample XHTML to XSL-FO stylesheet under the 'XHTML to XSL-FO' tab at http://www.antennahouse.com/antenna1/xml-to-xsl-fo-stylesheets/. There's also an XSL-FO tutorial available under the 'XML to XSL-FO' tab.

Generally, the XSL file for an XSL-FO conversion is not generated. You'll have to create this file yourself. It contains a lot of information not present in the XHTML, for example page layouts.
XSL-FO is a bit like CSS, yes. The difference is that XSL-FO has lots more options, so an XSL-FO file is 100 times longer than a CSS file.
Here's an introduction to XSL-FO.
And another tutorial.

Okay this site can give you some helps to generate xslfo site.
Abd if you wont the contrary this site is fine
XSL FO to HTML Converter

Generate PDF files using iText and apache velocity template(.vm)

What is the general workflow to generate a PDF using iText and an Apache Velocity template file (.vm) in Java?
I am interested in knowing steps like: parse template file, put Java object in context and steps to be performed to generate pdf etc.
I know this is a very basic question. But I am not able to find even a single example of this type on the web. I found XDocReport, but I am interested to know other alternatives as well.
Please help me with some sample project link or at least the steps to get started.

Yes, you can.
It all depends on how complex you want the PDFs to be.
Here are the steps for basic functionality
Generate a HTML file using Apache Velocity template file (.vm).
Use com.itextpdf.text.html.simpleparser.HTMLWorker (deprecated) to parse/convert that HTML file into a PDF.
Additionally, you can use com.itextpdf.text.pdf.PdfCopy.PageStamp to add content (borders, stamps, notes, annotations etc) to an existing PDF.
There is also com.itextpdf.tool.xml.XMLWorker for more advanced HTML conversion (adding style sheets etc)

Generating PDF using iText and an Apache Velocity template file (.vm) in Java directly is not possible because:
PDF is binary format,
Velocity generates plain text content.
On other words, Velocity cannot generate PDF.
XDocReport is able to generate a docx/odt report by merging a docx/odt template which contains some Velocity/Freemarker syntax with Java context. The generated docx/odt report can be convert it to pdf/xhtml.
It works because docx/odt are a zip which contains several xml entries. If you unzip a docx you will see word/document.xml. In this entry, you will see the content that you have typed with MS Word. word/document.xml is a plain text, so Velocity can be used in this case.
Here the XDocReport process to generate pdf from a docx template which uses Velocity:
Load docx template. this step consist to unzip the docx and stores in a map each xml entries (name entry as key and byte array as value). For instance map contains a key with word/document.xml and the xml content of this entry as value.
Loop for each xml entries which must be merged with Java context. For instance word/document.xml is merged with Java context by using Velocity and the result of merge replace the word/document.xml value of the map
Rebuild a new docx by zipping each entries of the map.
At this step we have a generated docx (the report).
To convert it to another format, XDocReport provides a docx-to-pdf converter based on Apache POI and iText. Here the XDocReport process to convert a docx to pdf:
Load docx with Apache POI
Loop for each structures of POI (XWPFParagraph, etc.) to create iText structure (iText Paragraph).
Note that XDocReport is modular and you can use other converters as well.

At first,we use freemarker template to generate a html file,and then render html to a pdf file by IItextRender .Finally, we can view pdf file in browser,there has a very useful javascript tools called pdfjs. Maybe you can try it.

Converting XML to PDF, using styles from XSL

I have following problem: I have a XML file with XSL stylesheet, that is rendering this XML file as neat table in HTML when I load it in web browser. Now I need to make a PDF that is looking EXACTLY like that XSL-styled XML in web browser, without need for making custom FO's for every file. Everything must be done in Java.

I need to make a PDF that is looking EXACTLY like that XSL-styled XML in web browser
Think again about this requirement. Paged media such as PDF and non-paged media such as HTML may only look "close enough", but never "exactly like" each other. This is even more obvious if you consider your HTML being displayed on devices with different screen sizes.
If you relax the above requirement somewhat, you'll probably agree that XSL-FO is the best choice. You definitely do not need to write "custom FO's for every file": write an XSLT just once, and use it on-the-fly to convert your XML to XSL-FO, and then use a rendering engine to process XSL-FO to PDF. Simple.

XSL-FO does sound like exactly what you need. But if that's not an option, first explicitly doing the XSLT transform on the XML in Java and then converting the resulting HTML (which by then is a String/byte array/DOM/whatever you want) to PDF using some additional library would do the trick. There's some libraries that support HTML to PDF, like iText for example. XSLT transformations in Java are really simple. Little code involved there.

Creating PDF, HTML, and optionally RTF documents from the same source using Java?

I was looking at using iText to create both a pdf and html version of a document with RTF as a possible option. According to this question this is no longer possible with iText. Is there a library that will allow me to create a document in Java and output it as both PDF and HTML? The ability to output RTF would be nice but is not required.

As that answer to the other question states, you can just use the iText RTF Library.

I have used PD4ML to convert HTML to pdf. Even though it is a commercial app. It is very reliable and supports CSS well.

JasperReports. If you look at this package it supports export to:
pdf
html
rtf
xls
xml
You have two options to create the documents:
via iReport - a visual designer for reports
via an API, where you construct everything with Java code.
Note that even though JasperReports's main function is to create reports, it can very well create other documents, with no tabular data for example.

You could also try Docmosis since that supports the output formats provided by OpenOffice (including the ones you specified) and you can often do the job with a lot less code.